Vitamin E kinetics and the function of tocopherol regulatory proteins

Minor bioactive lipids

Bioactive lipids-major and minor-comprise an array of compounds belonging to different chemical categories. Among the minor bioactive lipids carotenoids, sterols and tocochromanols attract continuously the interest of food scientists, nutritionists and medical doctors for their importance in food processing, preservation and for their health properties. Provitamin A and non-provitamin A carotenoids are found in various food sources of plant and animal origin and are added to foods as colorants. Their interactions with other food ingredients are critical because of their role against reactive oxygen species. The role of cholesterol through the diet after decades of disputes is better justified whereas at the same time emphasis is given to the technological and health aspects of phytosterols, which became very efficiently part of the daily diet for many population groups. Last but not least the importance of vitamin E is in a continuous debate for over 100years whereas studies on tocotrienols are intensified as a result of a transient to palm oil product consumption globally. Chemistry, natural occurrence, absorption and metabolism, dietary intake and dietary recommendations, major health impacts and key technological issues are updated and discussed with the support of recent findings.

Dietary vitamin E reaches the mitochondria in the flight muscle of zebra finches but only if they exercise

Whether dietary antioxidants are effective for alleviating oxidative costs associated with energy-demanding life events first requires they are successfully absorbed in the digestive tract and transported to sites associated with reactive species production (e.g. the mitochondria). Flying birds are under high energy and oxidative demands, and although birds commonly ingest dietary antioxidants in the wild, the bioavailability of these consumed antioxidants is poorly understood. We show for the first time that an ingested lipophilic antioxidant, α-tocopherol, reached the mitochondria in the flight muscles of a songbird but only if they regularly exercise (60 min of perch-to-perch flights two times in a day or 8.5 km day-1). Deuterated α-tocopherol was found in the blood of exercise-trained zebra finches within 6.5 hrs and in isolated mitochondria from pectoral muscle within 22.5 hrs, but never reached the mitochondria in caged sedentary control birds. This rapid pace (within a day) and extent of metabolic routing of a dietary antioxidant to muscle mitochondria means that daily consumption of such dietary sources can help to pay the inevitable oxidative costs of flight muscle metabolism, but only when combined with regular exercise.

Effects of Vitamin E and Coenzyme Q10 Supplementation on Oxidative Stress Parameters in Untrained Leisure Horses Subjected to Acute Moderate Exercise

The effects of antioxidant supplements on exercise-induced oxidative stress have not been investigated in untrained leisure horses. We investigated the effects of 14-day supplementation with vitamin E (1.8 IU/kg/day), coenzyme Q₁₀ (CoQ₁₀; ubiquinone; 800 mg/day), and a combination of both (the same doses as in mono-supplementation) on the blood levels of CoQ₁₀, vitamin E, and oxidative stress parameters in untrained leisure horses subjected to acute moderate exercise. Correlations between lipid peroxidation and muscle enzyme leakage were also determined. Forty client-owned horses were included in the study, with 10 horses in each of the antioxidant and placebo (paraffin oil) groups. Blood parameters were measured before supplementation, before and immediately after exercise, and after 24 h of rest. The differences in individual parameters between blood collection times and groups were analysed with linear mixed models (p ˂ 0.05). None of the supplemented antioxidants affected vitamin E and CoQ₁₀ concentrations, oxidative stress parameters, or serum muscle enzymes. Lipid peroxidation occurred in horses supplemented with placebo and CoQ₁₀ but not in horses supplemented with vitamin E or the combination of both antioxidants. These results suggest that vitamin E alone or in combination with CoQ₁₀ prevented lipid peroxidation in untrained leisure horses subjected to acute moderate exercise.

Safety Assessment of Tocopherols and Tocotrienols as Used in Cosmetics

The Cosmetic Ingredient Review (CIR) Expert Panel (Panel) assessed the safety of 14 tocopherols and tocotrienols and concluded these ingredients are safe as used in cosmetics. The tocopherols are reported to function in cosmetics as antioxidants or skin-conditioning agents; in contrast, tocotrienols are not reported to function as an antioxidants in cosmetics but as a light stabilizer, oral care agent, or skin-conditioning agent. The Panel reviewed the new and existing animal and clinical data to determine the safety of these ingredients and found it appropriate to extrapolate the existing information to conclude on the safety of all the tocopherols and tocotrienols.

Weight loss program is associated with decrease α-tocopherol status in obese adults

BACKGROUND & AIMS

Studies on changes in plasma α-tocopherol levels during body fat reduction in obese persons are not clear. The aim of the present study was to assess factors associated with α-tocopherol status in obese people and to examine changes in α-tocopherol status after a 6-week AntioxObesity weight loss program.

METHODS

The study was conducted in 60 overweight or obese adults, aged 18-54 years old. Food intake data were collected using the 3-day record method and a semi-quantitative food-frequency questionnaire. Anthropometric measurements included: height (H), body weight, waist circumference (WC) and hip circumference (HC), body composition: fat mass (FM) and fat-free mass (FFM), subcutaneous fat (SF) and visceral fat (VF). Lipid profile, α-tocopherol concentration, glutathione peroxidase (GPx) activity, total antioxidant capacity (TAC) in plasma and superoxide dismutase (SOD) activity in erythrocytes were determined.

RESULTS

Energy, fat, and carbohydrate intakes decreased significantly in all subjects (P < 0.001). Body weight, WC, body mass index (BMI), waist-to height ratio (WHtR), and FM, VF and SF decreased significantly during the 6 weeks in all subjects. Plasma α-tocopherol significantly decreased during the program (P = 0.006). No changes were observed for SOD activity, but GPx activity and TAC decreased significantly (P = 0.001; P = 0,023, respectively). Plasma α-tocopherol concentration after 6 weeks of the AntioxObesity program was strongly associated with baseline plasma α-tocopherol, changes in TC, VF and FM. Low α-tocopherol status (<20 μmol/L) was found in 78% of the women and 68% of the men, after 6 weeks of the AntioxObesity program. Men were characterized by a greater decrease in weight, BMI, WC, FM, VF, SF and TAC compared to women.

CONCLUSIONS

A 6-week weight loss program lowered α-tocopherol status in overweight and obese people. Low baseline α-tocopherol status and adiposity in obese adults negatively affected α-tocopherol status after 6 weeks weight loss program. These results, coupled with excessive weight and low α-tocopherol intake, led to the finding that there was an increased risk of oxidative stress diseases in adults on a reduced diet. Long-term dietary restriction program for obese patients should be monitored to avoid α-tocopherol deficiency, and take into account higher dietary α-tocopherol requirements for obese people.

Effect of combination vitamin E and single long-acting progesterone dose on enhancing pregnancy outcomes in the first two parities of young rabbit does

Vitamin E (Vit. E) is needed for young rabbits to prevent reproductive abnormalities, abortion and poor survivability of kits. Also, exogenous progesterone (P4) is needed for rabbits to enhance early embryonic development because of inadequate corpus luteum (CL) development at this age. Hence, the aim of this study was to investigate the effect of injecting Vit. E and the combination Vit. E+P4 in young does on live body weight (LBW) gain, gestation length (GL), numbers of services/conception (NS), conception rate (CR), abortion rate (AR), litter size (LS), kit weight (KW), total litter weight (TLW), mortality rate (MR) and progesterone (P4) concentration. The group treated with Vit. E+P4 had a greater LBW gain and lesser AR at first and second pregnancy. Treatments did not have significant impact on GL and LS in the first two parities. Treatments resulted in a significantly lesser MR and greater TLW at the second parity. The Vit. E+P4 treatment resulted in a significantly lesser NS at the first parity, while Vit. E alone resulted in a significant reduction in NS at the second parity. Vit. E+P4 had a positive effect on CR at the first parity compared with controls. Vit. E alone increased CR at the second parity compared with that of the control group. The mean P4 concentration from mating to mid-pregnancy at first parity was significantly greater in the Vit. E+P4 than Vit. E and control groups. In conclusion, treatment with Vit. E+P4 at the first parity may be economically applied on rabbit farms because this treatment resulted in a greater maintenance of the first pregnancy and improved reproductive performance at the second parity as compared with results from the Vit. E treated and control groups.

Transcriptomic effects of estradiol treatment on cultured human uterine smooth muscle cells

Contractility of the myometrial smooth muscle cells during the estrous cycle and pregnancy is modulated by estrogen but the temporal expression of estrogen (relative to progesterone) and the type of contraction involved are distinctly different in pregnancy and estrous. This in vitro cell culture study investigated the global gene expression profile of human uterine smooth muscle cells (hUtSMCs) following 17β-estradiol (E2) treatment. In response to E2 treatment 540 genes, many of which have not been previously described as estrogen responsive, were identified as significantly differentially expressed. These genes are involved in biological processes that include muscle contraction, cell migration and adhesion, apoptosis and phosphorylation. Evidence from this study suggests that 17β-estradiol may have effects that are contrary to an overall contraction phenotype. The hUtSMC in vitro culture system is a useful model to investigate steroid effects on smooth muscle cells and may provide additional clues as to how smooth muscle cells behave in vivo.

Dietary vitamin E affects α-TTP mRNA levels in different tissues of the Tan sheep

The α-tocopherol transfer protein (α-TTP) is a ~32kDa cytosolic protein that plays an important role in the efficient circulation of plasma α-tocopherol in the body, a factor with great relevance in reproduction. The α-TTP gene has been studied in a number of tissues; however, its expression and function in some ovine tissues remain unclear. A previous study from our laboratory has demonstrated α-TTP expression in sheep liver. In the present study we determined whether α-TTP is expressed in non-liver tissues and investigated the effects of dietary vitamin E on the α-TTP mRNA levels. Thirty-five male Tan sheep with similar body weight were randomly allocated into five groups and supplemented 0, 20, 100, 200 and 2000IUsheep(-1)day(-1) vitamin E, for four months, respectively. At the end of the study, the animals were slaughtered and tissue samples from the heart, spleen, lung, kidney, longissimus dorsi muscle and gluteus muscle were immediately collected. We found that the α-TTP gene is expressed in sheep tissues other than the liver. Moreover, dietary vitamin E levels had influenced the expression levels of α-TTP gene in these tissues in a tissue-specific way. The technique of immunohistochemistry was used to detect α-TTP in tissues of the heart, spleen, lung, and kidney and we found that α-TTP was mainly located in the cytoplasm while no α-TTP immunoreactivity was detected in the cytoplasm of longissimus dorsi and gluteus muscle samples. Importantly, our findings lay the foundation for additional experiments focusing on the absorption and metabolism of vitamin E in tissues other than the liver.

Vitamin E inhibits hepatic oxidative stress, toxicity and hyperproliferation in rats treated with the renal carcinogen ferric nitrilotriacetate

Ferric nitrilotriacetate (Fe-NTA) is a potent renal and hepatic tumor promoter, which acts through a mechanism involving oxidative stress. Fe-NTA when injected intraperitoneally into rats induces hepatic ornithine decarboxylase activity as well as hepatic DNA synthesis. Vitamin E is a well-known, lipid-soluble and chain-breaking antioxidant which protects cell membranes from peroxidative damage. In this study, we investigated the protective effect of vitamin E, a major fat-soluble antioxidant, against Fe-NTA-mediated hepatic oxidative stress, toxicity and hyperproliferation in Wistar rats. Animals were treated with two different doses of vitamin E for 1 week prior to Fe-NTA treatment. Vitamin E at a higher dose of 2.0 mg/animal/day showed significant reduction in Fe-NTA-induced hepatic ornithine decarboxylase activity, DNA synthesis, microsomal lipid peroxidation and hydrogen peroxide generation. Fe-NTA treatment alone caused depletion of glutathione, glutathione metabolizing and antioxidant enzymes in rat liver, whereas pretreatment of animals with vitamin E reversed these changes in a dose-dependent manner. Taken together, our results suggest that vitamin E may afford substantial protection against the damage caused by Fe-NTA exposure and can serve as a potent preventive agent to suppress oxidant-induced tissue injury.

Supplementation with natural forms of vitamin E augments antigen-specific TH1-type immune response to tetanus toxoid

This study compared the ability of three forms of vitamin E [tocotrienol-rich fraction (TRF), alpha-tocopherol (α-T), and delta-tocotrienol (δ-T3)] to enhance immune response to tetanus toxoid (TT) immunisation in a mouse model. Twenty BALB/c mice were divided into four groups of five mice each. The mice were fed with the different forms of vitamin E (1 mg) or vehicle daily for two weeks before they were given the TT vaccine [4 Lf] intramuscularly (i.m.). Booster vaccinations were given on days 28 and 42. Serum was collected (days 0, 28, and 56) to quantify anti-TT levels. At autopsy, splenocytes harvested were cultured with TT or mitogens. The production of anti-TT antibodies was augmented (P < 0.05) in mice that were fed with δ-T3 or TRF compared to controls. The production of IFN-γ and IL-4 by splenocytes from the vitamin E treated mice was significantly (P < 0.05) higher than that from controls. The IFN-γ production was the highest in animals supplemented with δ-T3 followed by TRF and finally α-T. Production of TNF-α was suppressed in the vitamin E treated group compared to vehicle-supplemented controls. Supplementation with δ-T3 or TRF can enhance immune response to TT immunisation and production of cytokines that promote cell-mediated (TH1) immune response.

Current knowledge on oxidative stress in hepatic ischemia/reperfusion

Ischemia/reperfusion (I/R) injury associated with hepatic resections and liver transplantation remains a serious complication in clinical practice, despite several attempts to solve the problem. The redox balance, which is pivotal for normal function and integrity of tissues, is dysregulated during I/R, leading to an accumulation of reactive oxygen species (ROS). Formation of ROS and oxidant stress are the disease mechanisms most commonly invoked in hepatic I/R injury. The present review examines published results regarding possible sources of ROS and their effects in the context of I/R injury. We also review the effect of oxidative stress on marginal livers, which are more vulnerable to I/R-induced oxidative stress. Strategies to improve the viability of marginal livers could reduce the risk of dysfunction after surgery and increase the number of organs suitable for transplantation. The review also considers the therapeutic strategies developed in recent years to reduce the oxidative stress induced by hepatic I/R, and we seek to explain why some of them have not been applied clinically. New antioxidant strategies that have yielded promising results for hepatic I/R injury are discussed.

Effects of vitamin e on bone biomechanical and histomorphometric parameters in ovariectomized rats

The present study examined the dose-dependent effect of vitamin E in reversing bone loss in ovariectomized (Ovx) rats. Sprague-Dawley rats were either Sham-operated (Sham) or Ovx and fed control diet for 120 days to lose bone. Subsequently, rats were divided into 5 groups (n = 12/group): Sham, Ovx-control, low dose (Ovx + 300 mg/kg diet; LD), medium dose (Ovx + 525 mg/kg diet; MD), and high dose (Ovx + 750 mg/kg diet; HD) of vitamin E and sacrificed after 100 days. Animals receiving MD and HD of vitamin E had increased serum alkaline phosphatase compared to the Ovx-control group. Bone histomorphometry analysis indicated a decrease in bone resorption as well as increased bone formation and mineralization in the Ovx groups supplemented with MD and HD of vitamin E. Microcomputed tomography findings indicated no effects of vitamin E on trabecular bone of fifth lumbar vertebrae. Animals receiving HD of vitamin E had enhanced fourth lumbar vertebra quality as evidenced by improved ultimate and yield load and stress when compared to Ovx-control group. These findings demonstrate that vitamin E improves bone quality, attenuates bone resorption, and enhances the rate of bone formation while being unable to restore bone density and trabecular bone structure.

Vitamin E deficiency in developing countries

In addition to its role as a potent antioxidant, vitamin E is involved in a wide range of physiological processes, ranging from immune function and control of inflammation to regulation of gene expression and cognitive performance. Results from multiple studies suggest that poor nutritional status and higher prevalence of other oxidative stressors such as malaria and HIV infection predispose populations in developing countries for vitamin E deficiency. Although direct comparison between study outcomes is complicated by varied definitions of vitamin E deficiency, data trends indicate that children and the elderly are more vulnerable age groups and that men may be at higher risk for deficiency than women. Public health initiatives aimed at improving the vitamin E status of high-risk populations in developing countries would be prudent to counteract oxidative stress, improve immune function, and protect against neurologic and cognitive deficits. Additional research is needed to establish dose-response relationships of various interventions and to develop cost-effective, culturally-appropriate, and targeted programs.

Effect of a Diet Supplemented with alpha-Tocopherol and beta-Carotene on ATP and Antioxidant Levels after Hepatic Ischemia-Reperfusion

Ischemia-reperfusion injury associated with liver transplantation remains a serious complication in clinical practice. In the present study the effect of intake of α-tocopherol or β-carotene to limit liver injury by oxidative stress in ischemia and reperfusion was explored. Wistar rats were fed with diets enriched with α-tocopherol (20 mg/day) or β-carotene (3 mg/day) for 21 days. After 21 days, their livers were subjected to 15 and 30 min of ischemia and afterwards were reperfused for 60 min. The recovery of levels of ATP during reperfusion was better in the group of rats whose diets were supplemented with α-tocopherol or β-carotene than in the group control. The supplementation of the diet induced changes in the profile of enzymatic antioxidants. The supplementation with α-tocopherol and β-carotene resulted in a decreased of superoxide dismutase during the ischemia and a recovery was observed after reperfusion. Not changes were observed for the enzymes catalase and glutathione peroxidase and glutathione but their values were higher to those of the group control. In conclusion, the supplementation with α-tocopherol and β-carotene improve the antioxidant and energetic state of liver after ischemia and reperfusion injury.

Effects of epigallocatechin gallate, L-ascorbic acid, alpha-tocopherol, and dihydrolipoic acid on the formation of deoxyguanosine adducts derived from lipid peroxidation

Oxidation of polyunsaturated fatty acids (PUFAs) releases alpha,beta-unsaturated aldehydes that modify deoxyguanosine (dG) to form cyclic 1,N(2)-propanodeoxyguanosine adducts. One of the major adducts detected in vivo is acrolein (Acr)-derived 1,N(2)-propanodeoxyguanosine (Acr-dG). We used a chemical model system to examine the effects of 4 antioxidants known to inhibit fatty acid oxidation on the formation of Acr-dG and 8-oxodeoxyguaonsine (8-oxodG) from the PUFA docosahexaenoic acid (DHA) under oxidative conditions. We found that epigallocatechin gallate (EGCG) and dihydrolipoic acid (DHLA) inhibit both Acr-dG and 8-oxodG formation. In contrast, ascorbic acid and alpha-tocopherol actually increase Acr-dG at high concentrations and do not show a concentration-dependant inhibition of 8-oxodG. We also studied their effects on blocking Acr-dG formation directly from Acr. EGCG and DHLA can both effectively block Acr-dG formation, but ascorbic acid and alpha-tocopherol show weak or little effect. These results highlight the complexity of antioxidant mechanisms and also reveal that EGCG and DHLA are effective at suppressing lipid peroxidation-induced Acr-dG and 8-oxodG formation as well as blocking the reaction of dG with Acr.

Tocopherol transfer protein sensitizes prostate cancer cells to vitamin E

Prostate cancer is a major cause of mortality in men in developed countries. It has been reported that the naturally occurring antioxidant α-tocopherol (vitamin E) attenuates prostate cancer cell proliferation in cultured cells and mouse models. We hypothesized that overexpression of the tocopherol transfer protein (TTP), a vitamin E-binding protein that regulates tocopherol status, will sensitize prostate cancer cells to the anti-proliferative actions of the vitamin. To test this notion, we manipulated the expression levels of TTP in cultured prostate cells (LNCaP, PC3, DU145, and RWPE-1) using overexpression and knockdown approaches. Treatment of cells with tocopherol caused a time- and dose-dependent inhibition of cell proliferation. Overexpression of TTP dramatically sensitized the cells to the apoptotic effects of α-tocopherol, whereas reduction ("knockdown") of TTP expression resulted in resistance to the vitamin. TTP levels also augmented the inhibitory effects of vitamin E on proliferation in semi-solid medium. The sensitizing effects of TTP were paralleled by changes in the intracellular accumulation of a fluorescent analog of vitamin E and by a reduction in intracellular levels of reactive oxygen species and were not observed when a naturally occurring, ligand binding-defective mutant of TTP was used. We conclude that TTP sensitizes prostate cancer cells to the anti-proliferative effects of vitamin E and that this activity stems from the ability of protein to increase the intracellular accumulation of the antioxidant. These observations support the notion that individual changes in the expression level or activity of TTP may determine the responsiveness of prostate cancer patients to intervention strategies that utilize vitamin E.

Breast milk tocopherol content during the first six months in exclusively breastfeeding Greek women

PURPOSE

To determine tocopherol and fat content of Greek mother's milk during the first 6 months of exclusive breastfeeding and correlate with maternal diet characteristics.

METHODS

Milk samples and dietary records were obtained by mothers at 1st (n = 64), 3rd (n = 39) and 6th (n = 23) month postpartum. Milk tocopherol content was determined by high-performance liquid chromatography method (HPLC) and fat content by the crematocrit method.

RESULTS

Milk's α-tocopherol content at 1st, 3rd and 6th month postpartum was 8.3 ± 3.4, 8.1 ± 4.2 and 8.5 ± 4.7 μmol/L, while total tocopherol values were 8.9 ± 3.6, 8.7 ± 4.6 and 9.5 ± 5.6 μmol/L, respectively, and were closely related to milk's fat content. No significant differences were observed for α- and total tocopherol content in breast milk among the three time points. Maternal vitamin E dietary intake was 7.2 ± 3.7, 6.8 ± 3.5 and 10.9 ± 5.2 mg/day at 1st, 3rd and 6th month postpartum, respectively. Though vitamin E dietary intake was less than the recommended one, vitamin E content in breast milk was considered sufficient for infant needs. Milk tocopherol content was found to be associated only with mothers' total fat and saturated fat dietary intake.

CONCLUSION

This study is among few in literature to determine tocopherol content of breast milk in European women and detect dietary factors that may influence its values. The only maternal dietary characteristic to affect breast milk tocopherol content was mothers' total fat intake, while tocopherol intake seems to have no effect.

Inhibitory activity of α-tocopherol on apoptosis in the rat bladder wall subjected to androgen deprivation

Alpha-tocopherol (2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-chromon-8-ol) is used in many previous urological studies. Thus to add to this knowledge in this study we studied the potential inhibitory activity on oxidative stress and process apoptosis on bladder wall in male rats subjected to androgen deprivation. A causal relationship between lower testosterone levels and apoptosis, as a component of castration-induced muscle atrophy, has been shown. Male Wistar rats (250-300 g) were used in this experiment, divided into four groups: control (sham operation; n=10); castration (n=10); castration, with alpha-tocopherol supplementation over preceding four weeks (n=10); and castration, with alpha-tocopherol supplementation over preceding four weeks and subsequent eight weeks (n=10). Activated caspase-3 was detected using a previously described technique, with analysis using stereological methodology. Nonparametric methods were used to test statistical significance, taking a significance level of P<0.005. This study was approved by the ethics committee of the university where the project was developed. The serum testosterone concentrations before castration were less than 20 pg/ml. Analysis of 8-isoprostane showed statistical significance (P<0.0003). The volumetric density of caspase-3 showed significant differences between the groups. There was no statistical significance regarding caspase-3 between sham and alpha-tocopherol plus castration or between the groups that received alpha-tocopherol supplementation. The observations showed that there was greater apoptosis in the group with castration alone than in the groups with alpha-tocopherol supplementation. This finding, together with the induced androgen deprivation and higher 8-isoprostane levels, corroborates the hypothesis that alpha-tocopherol supplementation has an important protective effect under conditions of oxidative stress, thereby avoiding the apoptotic process, especially regarding aging.

Oxidative stress and 8-oxoguanine repair are enhanced in colon adenoma and carcinoma patients

Oxidative stress is involved in the pathogenesis of colon cancer. We wanted to elucidate at which stage of the disease this phenomenon occurs. In the examined groups of patients with colorectal cancer (CRC, n = 89), benign adenoma (AD, n = 77) and healthy volunteers (controls, n = 99), we measured: vitamins A, C and E in blood plasma, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanine (8-oxoGua) in leukocytes and urine, leukocyte 8-oxoGua excision activity, mRNA levels of APE1, OGG1, 8-oxo-7,8-dihydrodeoxyguanosine 5'-triphosphate pyrophosphohydrolase (MTH1) and OGG1 polymorphism. The vitamin levels decreased gradually in AD and CRC patients. 8-OxodG increased in leukocytes and urine of CRC and AD patients. 8-OxoGua was higher only in the urine of CRC patients. 8-OxoGua excision was higher in CRC patients than in controls, in spite of higher frequency of the OGG1 Cys326Cys genotype, encoding a glycosylase with decreased activity. mRNA levels of OGG1 and APE1 increased in CRC and AD patients, which could explain increased 8-oxoGua excision rate in CRC patients. MTH1 mRNA was also higher in CRC patients. The results suggest that oxidative stress occurs in CRC and AD individuals. This is accompanied by increased transcription of DNA repair genes, and increased 8-oxoGua excision rate in CRC patients, which is, however, insufficient to counteract the increased DNA damage.

Pharmacokinetic evaluation of LASSBio-579: an N-phenylpiperazine antipsychotic prototype

This work aimed to investigate the pharmacokinetics of the N-phenylpiperazine antipsychotic prototype LASSBio-579 and to compare the results with those described for its bioisosteric derivative LASSBio-581. LASSBio-579 was administered to male Wistar rats as a 10 mg kg−1 intravenous bolus and 30 and 60 mg kg−1 intraperitoneal and 60 mg kg−1 oral doses, and plasma concentrations were determined by a validated LC-MS/MS method. Individual plasma concentration-time profiles were evaluated by non-compartmental and compartmental analysis, using WinNonlin. LASSBio-579 plasma protein binding was 93 ± 4%. After intravenous administration of 10 mg kg−1, the Vdss (0.6 ± 0.2 L kg−1) and the t1/2 (5.2 ± 1.1 h) determined were smaller than those obtained after extravascular routes, but the CLtot (0.23 ± 0.05 Lh−1 kg−1) was statistically similar (α = 0.05). The intraperitoneal and oral bioavailability was around 1.7% and 0.6%, respectively. The plasma profiles obtained after intravenous and intraperitoneal administration of the compound were best fitted to a three-compartment and two-compartment lag-time open model, respectively. Brain tissue showed low penetration (6.3%) and t1/2 of 1.1 h. Both the limited bioavailability and the lower brain penetration of LASSBio-579, in comparison with the LASSBio-581, suggest that its CNS activity may be due to a high receptor binding affinity or to a specific distribution into brain structures.

Anticancer actions of natural and synthetic vitamin E forms: RRR-alpha-tocopherol blocks the anticancer actions of gamma-tocopherol

Two naturally occurring dietary sources of vitamin E (i.e. RRR-alpha-tocopherol (alphaT) and RRR-gamma-tocopherol (gammaT)), the manufactured synthetic form of vitamin E, all-racemic-alpha-tocopherol (all-rac-alphaT), as well as a potent antitumor analog of vitamin E, RRR-alpha-tocopherol ether-linked acetic acid analog (alpha-TEA), were assessed for anticancer actions. Data showed that gammaT, all-rac-alphaT, and alpha-TEA but not alphaT or alphaT+gammaT significantly inhibited tumor burden of human MDA-MB-231 cells in nude mice. Immunohistochemical analyses of tumor tissue showed that all-rac-alphaT and alpha-TEA increased apoptosis and decreased proliferation in tumor cells while gammaT was associated with increased tumor cell apoptosis only. In vitro data showed alpha-TEA and gammaT but not all-rac-alphaT or alphaT to inhibit colony formation and induce apoptosis. Anticancer actions of alpha-TEA and gammaT involved death receptor 5 protein upregulation, Survivin protein downregulation and poly (ADP-ribose) polymerase cleavage, all of which were blocked by co-treatment with alphaT. In summary, both gammaT and alpha-TEA exhibited promising anticancer properties in vivo and in vitro, whereas all-rac-alphaT exhibited promising anticancer properties in vivo only. Importantly, alphaT not only failed to exhibit anticancer properties but it also reduced anticancer actions of gammaT in vivo and gammaT and alpha-TEA in vitro.

Changes inα-tocopherol and retinol levels during cardiopulmonary bypass correlate with maximal arterial partial pressure of oxygen

Cardiopulmonary bypass (CPB) is associated with oxidative stress. This study examined antioxidant levels in adults undergoing CPB surgery and their correlation with clinical variables. Arterial blood samples were obtained from 27 patients undergoing CPB. The time-course variation of vitamin C (spectrofluorimetry), alpha-tocopherol and retinol (HPLC) levels were determined. Plasma vitamin C rose initially but gradually decayed during reperfusion until 60% reduction of baseline values post-surgery. alpha-Tocopherol and retinol were reduced along CPB with post-operative values approximately 25% lower than baseline. No significant changes were found for selenium and glutathione peroxidase. PaO(2) values rose steadily throughout CPB. A correlation existed for alpha-tocopherol and retinol depletion vs maximal PaO(2) throughout CPB but no correlation was found for antioxidant consumption vs duration of ischaemia and reperfusion and hypothermia level. In conclusion, consumption of arterial blood antioxidant vitamins occurs with CPB in relation with PaO(2) levels but not for other clinical variables measured in this study.

Supplementation of coenzyme Q10 and alpha-tocopherol lowers glycated hemoglobin level and lipid peroxidation in pancreas of diabetic rats

The importance of nutritional supplementation in diabetes remains an unresolved issue. The present study was undertaken to examine the effects of alpha-tocopherol and CoQ(10), powerful antioxidants, on metabolic control and on the pancreatic mitochondria of GK rats, a model of type 2 diabetes. We also evaluated the efficacy of these nutrients in preventing the diabetic pancreatic lesions observed in GK rats. Rats were divided into 4 groups, a control group of diabetic GK rats and 3 groups of GK rats administered with alpha-tocopherol and CoQ(10) alone or both in association, during 8 weeks. Fasting blood glucose levels were not significantly different between the groups, nor were blood glucose levels at 2 hours after a glucose load. HbA1c level was significantly reduced in the group supplemented with both antioxidants. Diabetes induced a decrease in coenzyme Q plasma levels that prevailed after treatment with antioxidants. In addition, the plasma alpha-tocopherol levels were higher after treatment with the antioxidants. An increment in some components of the antioxidant defense system was observed in pancreatic mitochondria of treated GK rats. Moreover, the antioxidants tested either alone or in association failed to prevent the pancreatic lesions in this animal model of type 2 diabetes. In conclusion, our results indicate that CoQ(10) and alpha-tocopherol decrease glycated HbA1c and pancreatic lipid peroxidation. These antioxidants increase some components of the antioxidant defense system but do not prevent pancreatic lesions. Thus, we cannot rule out the potential benefit of antioxidant treatments in type 2 diabetes in the prevention of their complications.

The effect of muscle-damaging exercise on blood and skeletal muscle oxidative stress: magnitude and time-course considerations

The aim of this article is to present the effects of acute muscle-damaging exercise on oxidative stress/damage of animal and human tissues using a quantitative approach and focusing on the time-course of exercise effects. The reviewed studies employed eccentric contractions on a dynamometer or downhill running. The statistical power of each study to detect a 20% or 40% post-exercise change compared with pre-exercise value in each oxidative stress/damage biomarker was calculated. Muscle-damaging exercise can increase free radical levels and augment oxidation of lipids, proteins, glutathione and possibly DNA in the blood. In contrast, the effect of muscle-damaging exercise on concentration of antioxidants in the blood, except for glutathione, was little. Muscle-damaging exercise induces oxidative stress/damage in skeletal muscle, even though this is not fully supported by the original statistical analysis of some studies. In contrast, muscle-damaging exercise does not appear to affect--at least to similar extent as the oxidative stress/damage markers--the levels of antioxidants in skeletal muscle. Based on the rather limited data available, the oxidative stress response of skeletal muscle to exercise was generally independent of muscle fibre type. Most of the changes in oxidative stress/damage appeared and were sustained for days after muscle-damaging exercise. The major part of the delayed oxidative stress/damage production that follows muscle-damaging exercise probably comes from phagocytic cells that are activated and recruited to the site of the initial damage. A point that emerged and potentially explains much of the lack of consensus among studies is the low statistical power of many of them. In summary, muscle-damaging exercise can increase oxidative stress/damage in blood and skeletal muscle of rats and humans that may persist for and/or appear several days after exercise.

Vitamin E in human health and disease

Vitamin E in nature is comprised of a family of tocopherols and tocotrienols. The most studied of these is alpha-tocopherol (alpha-TOH), because this form is retained within the body, and vitamin E deficiency is corrected with this supplement. alpha-TOH is a lipid-soluble antioxidant required for the preservation of cell membranes, and it potentially acts as a defense against oxidative stress. Many studies have investigated the metabolism, transport, and efficacy alpha-TOH in the prevention of sequelae associated with cardiovascular disease (CVD). Supplementation with vitamin E is considered to provide health benefits against CVD through its antioxidant activity, the prevention of lipoprotein oxidation, and the inhibition of platelet aggregation. However, the results from large prospective, randomized, placebo-controlled clinical trials with alpha-TOH have been largely negative. A recent meta-analysis suggests that alpha-TOH supplements may actually increase all-cause mortality; however, the mechanism for this increased risk is unknown. In vitro studies performed in human cell cultures and animal models suggest that vitamin E might increase the hepatic production of cytochrome P450s and MDR1. Induction of CYP3A4 or MDR1 by vitamin E could potentially lower the efficacy of any drug metabolized by CYP3A4 or MDR1. Other possibilities include an adverse effect of alpha-TOH on blood pressure in high-risk populations. Because of the wide popularity and use of vitamin E supplements, further research into potential adverse effects is clearly warranted.

Dose-dependent modulation of systemic lipid peroxidation and activity of anti-oxidant enzymes by vitamin E in the rat

The objective of this work was to examine the time-dependent pro-oxidant versus antioxidant effect of various doses of vitamin E used commonly in experimental studies. Erythrocyte activity of superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase (CAT) and plasma lipid peroxidation levels were investigated following biweekly intramuscular administration of 100, 300 and 600 mg/kg of vitamin E at a baseline time point, and additionally at 2, 4 and 6 weeks after initiating treatment. Vitamin E had an antioxidant effect when administered at low doses over short time periods, and increased the activity of antioxidant enzymes. At higher doses and over longer time periods, it increased the level of lipid peroxidation, and attenuated the activity of antioxidant enzymes. These results suggest that time-dependent variations in vitamin E effects should be considered in design and interpretation of experimental antioxidant studies, as well as during clinical trials.

Chemical reactivities and physical effects in comparison between tocopherols and tocotrienols: physiological significance and prospects as antioxidants

Vitamin E is a generic term for all tocopherol and tocotrienol derivatives. The most abundant and active form of vitamin E isoforms in vivo is alpha-tocopherol, but recently the roles of other forms of vitamin E have received renewed attention. In this review, we summarize the differences among alpha-, beta-, gamma-, delta-tocopherols and tocotrienols specifically regarding the following points; (i) their radical-scavenging efficacies and chemical reactivity with metal ions in solution, (ii) their physical effects at the liposomal membrane interior, and (iii) their protective effects against cell toxicity. Moreover, the physiological significance and future prospects for using vitamin E, especially tocotrienols, for the prevention and treatment of disease are discussed.

Novel transcriptional activities of vitamin E: inhibition of cholesterol biosynthesis

Vitamin E is a dietary lipid that is essential for vertebrate health and fertility. The biological activity of vitamin E is thought to reflect its ability to quench oxygen- and carbon-based free radicals and thus to protect the organism from oxidative damage. However, recent reports suggest that vitamin E may also display other biological activities. Here, to examine possible mechanisms that may underlie such nonclassical activities of vitamin E, we investigated the possibility that it functions as a specific modulator of gene expression. We show that treatment of cultured hepatocytes with (RRR)-alpha-tocopherol alters the expression of multiple genes and that these effects are distinct from those elicited by another antioxidant. Genes modulated by vitamin E include those that encode key enzymes in the cholesterol biosynthetic pathway. Correspondingly, vitamin E caused a pronounced inhibition of de novo cholesterol biosynthesis. The transcriptional activities of vitamin E were mediated by attenuating the post-translational processing of the transcription factor SREBP-2 that, in turn, led to a decreased transcriptional activity of sterol-responsive elements in the promoters of target genes. These observations indicate that vitamin E possesses novel transcriptional activities that affect fundamental biological processes. Cross talk between tocopherol levels and cholesterol status may be an important facet of the biological activities of vitamin E.

Retinol, carotenoids, and tocopherols in the milk of lactating adolescents and relationships with plasma concentrations

OBJECTIVE

We determined the concentrations of retinol, carotenoids, and tocopherols in breast milk of adolescents and evaluated their associations with plasma levels and with maternal characteristics (period of lactation, body mass index, age of menarche, and years postmenarche).

METHODS

This was a single cross-sectional survey of retinol, carotenoid, and tocopherol composition of milk and plasma of lactating adolescent mothers (n = 72; 30-120 d postpartum) attending public daycare clinics in Rio de Janeiro, Brazil. Milk and plasma components were analyzed by high-performance liquid chromatography.

RESULTS

Nutrient concentrations (micromoles per liter, mean +/- SE) in plasma and milk were, respectively, retinol 2.1 +/- 0.5 and 0.62 +/- 0.44, beta-carotene 0.18 +/- 0.19 and 0.016 +/- 0.017, alpha-carotene 0.05 +/- 0.04 and 0.0035 +/- 0.002, lutein plus zeaxanthin 0.15 +/- 0.11 and 0.025 +/- 0.024, lycopene 0.1 +/- 0.11 and 0.016 +/- 0.025, alpha-tocopherol 10.8 +/- 5.3 and 2.7 +/- 1.8, gamma-tocopherol 2.6 +/- 2.3 and 0.37 +/- 0.15. The milk/plasma molar ratios of retinol and tocopherols were two times higher than those of carotenoids. Significant correlations (P < 0.001) between milk and plasma nutrient levels were observed for beta-carotene (r = 0.41), alpha-carotene (r = 0.60), and lutein plus zeaxanthin (r = 0.57), but not for lycopene, retinol, and tocopherols. Nutrient concentrations in plasma and in milk were not associated with the maternal characteristics investigated.

CONCLUSION

Concentrations of the nutrients studied, especially retinol and alpha-tocopherol, in mature milk of lactating adolescents were, in general, lower than in milk of adult lactating women. Milk concentrations were associated with plasma concentrations only for beta-carotene, alpha-carotene, and lutein plus zeaxanthin.

Vitamin E and selenium supplementation and risk of prostate cancer in the Vitamins and lifestyle (VITAL) study cohort

OBJECTIVE

Vitamin E and selenium are promising nutrients for the prevention of prostate cancer, and both are currently being tested in a large randomized trial for prostate cancer. However, results are not expected for at least 6 years. We aimed to investigate the association of vitamin E and selenium supplementation with prostate cancer in the VITamins And Lifestyle (VITAL) study, a cohort study specifically designed to examine supplement use and future cancer risk.

METHODS

In a prospective design, 35,242 men recruited between 2000 and 2002 from western Washington State completed a questionnaire, including detailed questions about vitamin E and selenium supplement intake during the past 10 years from brand-specific multivitamins and single supplements. Using linkage to the western Washington SEER cancer registry, we documented 830 new cases of prostate cancer from baseline through December 2004.

RESULTS

A 10-year average intake of supplemental vitamin E was not associated with a reduced prostate cancer risk overall [hazard ratio (HR) 0.86, 95% confidence interval (CI) 0.65-1.1 for > or =400 IU/day vs. non-use, p for trend 0.36]; however, risk for advanced prostate cancer (regionally invasive or distant metastatic, n = 123) decreased significantly with greater intake of supplemental vitamin E (HR 0.43, 95% CI 0.19-1.0 for 10-year average intake > or =400 IU/day vs. non-use, p for trend 0.03). There was no association between selenium supplementation and prostate cancer risk (HR 0.90, 95% CI 0.62-1.3 for 10-year average intake >50 microg/day vs. non-use, p for trend 0.97).

CONCLUSIONS

In this prospective cohort, long-term supplemental intake of vitamin E and selenium were not associated with prostate cancer risk overall; however, risk of clinically relevant advanced disease was reduced with greater long-term vitamin E supplementation.

Reduced expression of alpha-tocopherol-associated protein is associated with tumor cell proliferation and the increased risk of prostate cancer recurrence

AIM

To examine the impact and prognostic significance of alpha-tocopherol associated protein (TAP) expression in a series of prostate cancer patients.

METHODS

Tissues from 87 patients underwent radical prostatectomy were examined for TAP expression by immunohistochemistry. The relationships of the staining results, the clinic pathological characteristics and the recurrence times were analyzed.

RESULTS

Compared with the adjacent areas of normal and benign glands, immunoreactivity of TAP was reduced in areas of prostate cancer. A lower TAP-positive cell number per mm(2) of the largest cancer area (defined as TAP-PN) was associated with higher clinical stage (r = -0.248, P = 0.0322). Inverse associations were found among the TAP-PN and positive lymph nodes (r = -0.231, P = 0.0325), preoperative prostate-specific antigen (PSA) levels (r = -0.423, P = 0.0043), tumor size (r= -0.315, P= 0.0210) and elevated tumor cell proliferation, which was indicated by the staining of Ki-67 (r = -0.308, P = 0.0026). TAP-PN was a significant predictor of recurrence univariately (P = 0.0006), as well as multivariately, adjusted for known markers including preoperative PSA, clinical stage, Gleason score, surgical margin, extra-prostatic extension, seminal vesicle invasion and lymph node metastasis (P = 0.0012).

CONCLUSION

Reduced expression of TAP was associated with the cell proliferation status of prostate cancer, adverse pathological parameters and the increased risk of recurrence.

Tocotrienols in health and disease: the other half of the natural vitamin E family

Tocochromanols encompass a group of compounds with vitamin E activity essential for human nutrition. Structurally, natural vitamin E includes eight chemically distinct molecules: alpha-, beta-, gamma- and delta-tocopherol; and alpha-, beta-, gamma- and delta-tocotrienol. Symptoms caused by alpha-tocopherol deficiency can be alleviated by tocotrienols. Thus, tocotrienols may be viewed as being members of the natural vitamin E family not only structurally but also functionally. Palm oil and rice bran oil represent two major nutritional sources of natural tocotrienol. Taken orally, tocotrienols are bioavailable to all vital organs. The tocotrienol forms of natural vitamin E possesses powerful hypocholesterolemic, anti-cancer and neuroprotective properties that are often not exhibited by tocopherols. Oral tocotrienol protects against stroke-associated brain damage in vivo. Disappointments with outcomes-based clinical studies testing the efficacy of alpha-tocopherol need to be handled with caution and prudence recognizing the untapped opportunities offered by the other forms of natural vitamin E. Although tocotrienols represent half of the natural vitamin E family, work on tocotrienols account for roughly 1% of the total literature on vitamin E. The current state of knowledge warrants strategic investment into investigating the lesser known forms of vitamin E.

γ-Tocopherol as a possible marker for nutrition-related risk: results from four National Diet and Nutrition Surveys in Britain

Relationships between vitamin E status (α and γ-tocopherol and their ratio in plasma), anthropometric and biochemical indices, and food and nutrient intakes, were studied in four British National Diet and Nutrition Surveys: children aged 1·5–4·5 years, young people aged 4·0–18·0 years, adults 19·0–64·0 years and adults aged ≥65·0 years. γ-Tocopherol:α-tocopherol ratio declined with age. In older women γ-tocopherol and γ-tocopherol:α-tocopherol ratios were directly related to indices of obesity. In young men α- and γ-tocopherols were directly correlated with obesity, but γ-tocopherol:α-tocopherol ratio was not. For young people and toddlers, fewer obesity indices were available and relationships were weaker. Other fat- and water-soluble vitamin indices correlated directly with α-tocopherol and inversely with γ-tocopherol and γ-tocopherol:α-tocopherol ratio. Whereas α-tocopherol correlated directly with ‘healthy’ nutrient choices (such as intrinsic sugars, dietary fibre, vitamins and potassium) and inversely with ‘unhealthy’ choices (extrinsic sugars and monounsaturated fats, i.e. avoidance of polyunsaturated fat), γ-tocopherol and the γ-tocopherol:α-tocopherol ratio related inversely with ‘healthy’ choices. Food groups had analogous relationships; thus, α-tocopherol related directly to use of polyunsaturated fats, fresh fruits and fruit juices, and inversely to non-polyunsaturated fats and extrinsic sugar. The reverse was true for γ-tocopherol and γ-tocopherol:α-tocopherol ratio. Although the mechanisms underlying these relationships are obscure, the γ-tocopherol:α-tocopherol ratio may reveal poor dietary choices, status predictors and a propensity for obesity in later life, especially in women.

Triton WR1339, an inhibitor of lipoprotein lipase, decreases vitamin E concentration in some tissues of rats by inhibiting its transport to liver

The aim of this experiment was to clarify the contribution of the alpha-tocopherol transfer activity of lipoprotein lipase (LPL) to vitamin E transport to tissues in vivo. We studied the effect of Triton WR1339, which prevents the catabolism of triacylglycerol-rich lipoproteins by LPL on vitamin E distribution in rats. Vitamin E-deficient rats fed a vitamin E-free diet for 4 wk were injected with Triton WR1339 and administered by oral gavage an emulsion containing 10 mg of alpha-tocopherol, 10 mg of gamma-tocopherol, or 29.5 mg of a tocotrienol mixture with 200 mg of sodium taurocholate, 200 mg of triolein, and 50 mg of albumin. alpha-Tocopherol was detected in the serum and other tissues of the vitamin E-deficient rats, but gamma-tocopherol, alpha- and gamma-tocotrienol were not detected. Triton WR1339 injection elevated (P<0.05) the serum alpha-tocopherol concentration and inhibited (P<0.05) the elevation of alpha-tocopherol concentration in the liver, adrenal gland, and spleen due to the oral administration of alpha-tocopherol. Neither alpha-tocopherol administration nor Triton WR1339 injection affected (P>or=0.05) the alpha-tocopherol concentration in the perirenal adipose tissue, epididymal fat, and soleus muscle despite a high expression of LPL in the adipose tissue and muscle. These data show that alpha-tocopherol transfer activity of LPL in adipose tissue and muscle is not important for alpha-tocopherol transport to the tissue after alpha-tocopherol intake or that the amount transferred is small relative to the tissue concentration. Furthermore, Triton WR1339 injection tended to elevate the serum gamma-tocopherol (P=0.071) and alpha-tocotrienol (P=0.053) concentrations and lowered them (P<0.05) in the liver and adrenal gland of rats administered gamma-tocopherol or alpha-tocotrienol. These data suggest that lipolysis of triacylglycerol-rich chylomicron by LPL is necessary for postprandial vitamin E transport to the liver and subsequent transport to the other tissues.

The use of Raman microscopy to determine and localize vitamin E in biological samples

Alpha-tocopherol (aT), the predominant form of vitamin E in mammals, is thought to prevent oxidation of polyunsaturated fatty acids. In the lung, aT is perceived to be accumulated in alveolar type II cells and secreted together with surfactant into the epithelial lining fluid. Conventionally, determination of aT and related compounds requires extraction with organic solvents. This study describes a new method to determine and image the distribution of aT and related compounds within cells and tissue sections using the light-scattering technique of Raman microscopy to enable high spatial as well as spectral resolution. This study compared the nondestructive analysis by Raman microscopy of vitamin E, in particular aT, in biological samples with data obtained using conventional HPLC analysis. Raman spectra were acquired at spatial resolutions of 2-0.8 microm. Multivariate analysis techniques were used for analyses and construction of corresponding maps showing the distribution of aT, alpha-tocopherol quinone (aTQ), and other constituents (hemes, proteins, DNA, and surfactant lipids). A combination of images enabled identification of colocalized constituents (heme/aTQ and aT/surfactant lipids). Our data demonstrate the ability of Raman microscopy to discriminate between different tocopherols and oxidation products in biological specimens without sample destruction. By enabling the visualization of lipid-protein interactions, Raman microscopy offers a novel method of investigating biological characterization of lipid-soluble compounds, including those that may be embedded in biological membranes such as aT.

Tocotrienols: the emerging face of natural vitamin E

Natural vitamin E includes eight chemically distinct molecules: alpha-, beta-, gamma-, and delta-tocopherols and alpha-, beta-, gamma-, and delta-tocotrienols. More than 95% of all studies on vitamin E are directed toward the specific study of alpha-tocopherol. The other forms of natural vitamin E remain poorly understood. The abundance of alpha-tocopherol in the human body and the comparable efficiency of all vitamin E molecules as antioxidants led biologists to neglect the non-tocopherol vitamin E molecules as topics for basic and clinical research. Recent developments warrant a serious reconsideration of this conventional wisdom. The tocotrienol subfamily of natural vitamin E possesses powerful neuroprotective, anticancer, and cholesterol-lowering properties that are often not exhibited by tocopherols. Current developments in vitamin E research clearly indicate that members of the vitamin E family are not redundant with respect to their biological functions. alpha-Tocotrienol, gamma-tocopherol, and delta-tocotrienol have emerged as vitamin E molecules with functions in health and disease that are clearly distinct from that of alpha-tocopherol. At nanomolar concentration, alpha-tocotrienol, not alpha-tocopherol, prevents neurodegeneration. On a concentration basis, this finding represents the most potent of all biological functions exhibited by any natural vitamin E molecule. Recently, it has been suggested that the safe dose of various tocotrienols for human consumption is 200-1000/day. A rapidly expanding body of evidence supports that members of the vitamin E family are functionally unique. In recognition of this fact, title claims in publications should be limited to the specific form of vitamin E studied. For example, evidence for toxicity of a specific form of tocopherol in excess may not be used to conclude that high-dosage "vitamin E" supplementation may increase all-cause mortality. Such conclusion incorrectly implies that tocotrienols are toxic as well under conditions where tocotrienols were not even considered. The current state of knowledge warrants strategic investment into the lesser known forms of vitamin E. This will enable prudent selection of the appropriate vitamin E molecule for studies addressing a specific health need.

The α‐Tocopherol Transfer Protein

Almost a century ago, plant extracts were documented to be critical for the fertility of rodents. This activity was later ascribed to vitamin E, a term comprising a number of structurally related plant lipids that function as fat soluble antioxidants. The alpha-tocopherol transfer protein (TTP) is a critical regulator of vitamin E status that stimulates the movement of vitamin E between membrane vesicles in vitro and facilitates the secretion of tocopherol from hepatocytes. Heritable mutations in the ttpA gene cause ataxia with vitamin E deficiency (AVED), an autosomal recessive disorder characterized by low plasma vitamin E levels and progressive neurodegeneration. This chapter summarizes recent advances in our understanding of the molecular and physiological aspects of TTP activity.

Natural vitamin E alpha-tocotrienol: retention in vital organs in response to long-term oral supplementation and withdrawal

The natural vitamin E tocotrienol (TCT) possesses biological properties not shared by tocopherols (TCP). Nanomolar alpha-TCT, not alpha-TCP, is potently neuroprotective (JBC 275:13049; 278:43508; Stroke 36:2258). The report that the affinity of TTP to bind (alpha-TCT is an order of magnitude lower than that for alpha-TCP questions the bioavailability of orally taken TCT to tissues. Oral supplementation of TCT for 3 years in nine generations of female and male rat was studied. Ten vital organs were examined. To gain insight into the turnover of alpha-TCT in tissues, a subset of supplemented rats was moved to vitamin E deficient diet for 7 weeks. Orally supplemented alpha-TCT was delivered to all vital organs including the brain and spinal cord in significant amounts. In organs such as the skin, adipose and gonads the maximum level of alpha-TCT achieved in response to supplementation was folds higher than baseline values of alpha-TCP in rats maintained on laboratory chow. Females had higher levels of alpha-TCT compared to matched tissues of corresponding males. To gain insight into how quickly alpha-TCT is metabolized in the tissues, washout of alpha-TCT from vital organs was examined. alpha-TCT accumulated in vital organs over more than 2 years was almost completely lost in less than 2 months when the supplementation was stopped. This is in sharp contrast with findings related to alpha-TCP retention. The ability of long-term oral supplementation to maintain and elevate alpha-TCT levels in vital organs together with the rapid elimination of the intact vitamin from all organs studied underscores the need for continuous oral supplementation of TCT.

Dietary agents in the chemoprevention of prostate cancer

Nutritional factors have been estimated to contribute 20-60% of cancers around the globe, and almost one-third of deaths are being reported in Western countries. According to estimates by the American Cancer Society, during the year 2005 about 232,090 new cases of prostate cancer will be diagnosed alone in the United States and 30,350 men will die of this disease. The high incidence and long latency period of prostate cancer offer plenty of time to pursue strategies toward prevention and/or treatment to suppress or revert this disease. Epidemiological evidence suggests that plant-based dietary agents decrease the risk of some types of human cancer, including prostate cancer. Intake of 400-600 g/day of fruits and vegetables is associated with reduced risk of several cancers. The use of micronutrients and/or other phenolic agents in the diet or synthetic exogenous supplements to prevent neoplastic transformation of normal cells or to slow the progression of established malignant changes in cancer cells is termed "chemoprevention." Considerable attention has been devoted to identify plant-based dietary agents that may serve as natural inhibitors of prostate carcinogenesis. Much progress has been made in the last decade in this area of investigation through identification of pathways that play important roles in prostate tumorigenesis. This article summarizes epidemiological, clinical, and mechanistic studies and the significance of plant-derived dietary agents such as flavonoids, indoles, isothiocyanates, phenolics, monoterpenes, and complementary and alternative agents in the management of prostate cancer with recommendations for future studies to advance this area of research.